NOTE: The "Custom Admin Bar" plugin is not available in the drop-down menu of plugins to select for this topic.
Ideally, this is a feature request: Change the default URL for the Entry Title text or graphic in the Custom Admin Bar to the home page of the primary site. Or better yet, provide an admin field for assigning a link.
Example: The edublogs logo in this screenshot should link to the edublogs homepage (or link assigned via admin field) instead of reloading the current page. Optionally, clicking it should do nothing at all.
In the meantime, how might one change the link for the graphic or text assigned as the Entry Title?